supplementary materials

(Thiocyanato-S)tris(thiourea-S)mercury(II) chloride

In the title salt, [Hg(NCS)(CH4N2S)3]Cl, the Hg2+ ion is coordinated in a severely distorted tetrahedral manner by three thiourea groups and one thiocyanate anion through their S atoms. The S-Hg-S angles vary widely from 87.39 (5) to 128.02 (4)°. Weak intramolecular N-HS hydrogen bonds are observed, which form S(6) ring motifs. In the crystal, the ions are linked by N-HN and weak N-HCl interactions, generating a three-dimensional network.

This work is part of a research project concerning the investigation of thiourea
(N2H4CS) and thiocyanate (SCN) based metal organic crystalline materials
and their derivatives (Ramesh et al., 2012). Transition metal
thiourea
and thiocyanate coordination complexes are candidate materials for device
applications including their nonlinear optical properties. As ligands, both
thiourea and thiocyanate are interesting due to their potential formation of
metalcoordination complexes as they exhibit multifunctional coordination modes
due to the presence of 'S' and 'N' donor atoms. With reference to the hard and
soft acids and bases) concept (Ozutsmi et al., 1989; Bell et
al.,
2001), thesoft cations show a pronounced affinity for coordination with
the
softer ligands, while hard cations prefer coordination with harder ligands.
Several crystallographic reports about mercury(II) complexes usually consist
of discrete monomeric molecules with tetrahedral (somewhat distorted)
coordination environments around mercury(II) (Nawaz et al.,
2010).
Here, we report the synthesis and structure of the title salt,
[(SC(2NH2))3(SCN-)Hg(2+]+ . Cl-,(I).

In (I), the Hg2+ ion is coordinated to three softer S atoms of thiourea and
one softer S atom of a thiocyanate anion in addition to the isolated chlorine
ion (Fig. 1). Intramolecular N—H···S hydrogen bonds are observed which form
S(6) ring motifs (Bernstein et al., 1995). Bond distances and
angles
are in agreement with those reported for related compounds (Safari et
al., 2009; Nawaz et al., 2010). The S—Hg—S
angles vary widely
from 87.39 (5)° to 128.02 (4)°, indicative of a distorted tetrahedral
arrangement. The SCN- moiety is planar [to within 0.007 (1) Å] with the
C—N and C—S bond lengths corresponding to the values intermediate between
single and double bonds. The S2—C4—N7 unit is nearly linear with a bond
angle of 177.9 (6)°. In the crystal, the ions are stabilized by weak
N—H···Cl, and N—H···N intermolecular interactions (Table.1) which form
a three-dimensional network (Fig. 2).

A mixture of thiourea, ammonium thiocyanate and mercury (II) choloride were
dissolved in aqueous solution in the molar ratio 3:1:1 and thoroughly mixed
for an hour to obtain a homogenous mixture. The solution was allowed to
evaporate slowly at ambient temperature. Colourless single crystals suitable
for single-crystal XRD were obtained in 12 days.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger.

The authors thank Dr Babu Vargheese, SAIF, IIT, Madras, India, for his help in
collecting the X-ray intensity data. KR thanks the University Grants
Commission, Government of India, for financial support granted under a Major
Research Project [F. No.41–1008/2012 (SR)].